Fabrication of fluidic pumping devices, and more particularly fabrication of valves in such pumping devices, is a difficult aspect in the development of microfluidic systems.
Various efforts have been undertaken in order to develop such pumps. For instance U.S. Pat. No. 7,090,471 shows a possible implementation, an embodiment of which is illustrated in FIG. 1. A valve device of fluid regulating element 10 is disposed on a substrate 11. The fluid regulating element 10 includes a fluid channel 12 including an inlet 13 at a first end for receiving a liquid and an outlet 14 at a second end, the fluid channel 12 being disposed overlying the substrate 11. An actuation region 15 filled with air is disposed overlying the substrate 11 and coupled to the fluid channel 12. A polymer based diaphragm 16 is coupled between the fluid channel 12 and the actuation region 15. A first electrode 17 is coupled to the substrate 11 and to the actuation region 15. A second electrode 18 is coupled to the polymer based diaphragm 16. An electrical power source is coupled between the first electrode 17 and the second electrode 18 to create an electrostatic field between the first and second electrodes 17, 18. When applying such potential difference, the air in the actuation region 15 is being compressed, which causes the polymer-based diaphragm 16 to move towards the substrate 11, thus generating an under pressure in the fluid channel 12 and acting as an active, i.e. controlled, valve for the fluid channel 12.
In the above solution, actuation force is restricted by the electrode plate area, as the active part of the electrode plate area is constrained by the channel width. In other words, the actuation force is restricted by the projection of the electrode plate area on the channel wall. Further, in the above solution the fluid channel cannot be completely closed.
WO 96/17172 discloses an integrated electrical discharge microactuator, in which an electric field is generated between electrodes, which electric field generates an electrical discharge in a gas (working fluid) in a chamber. This electrical discharge modifies the state parameters (e.g., temperature, density, pressure, and speed) of the gas, and such modification provides a deformation of a common membrane between a working chamber and a pumping chamber. In this microactuator, the pumping chamber cannot be completely closed.